Automatic steering apparatus



Y' Z, 1947- r v. H. SEVERY 2,424,288

I I AUTOMATIC STEERING APPARATUS Filed March 24, 1944 2 Sheets-Sheet 133 :4 as as 62 -58 5 6/ I mrurlsRQx/ M 3 July 22, 1947. v. H. SEVERYAUTOMATIC STEERING APPARATUS Filed March 24, 1944 2 Sheets-Sheet 2Patented July 22, 1947 UNITED STATES PATENT ornce AUTOMATIC STEERINGAPPARATUS Victor H. Severy, Atlanta, Ga.

Application March 24, 1944, Serial No. 528,002

8 Claims. (Cl. ISO-79.2)

This invention relates to a method and apparatus for effecting theautomatic steering of a vehicle running along a roadway, to maintain thevehicle in the middle of the roadway or in the middle of the lane onwhich the vehicle should run.

An object of the invention is to provide a simple method and apparatusfor utilizing a guidestrip extending along the middle of the lane, tocontrol the steering apparatus of the vehicle, such as an automobile ortruck, in such a way as to maintain the vehicle in line directly overthe guide-strip.

In practicing the invention I provide a guide strip extending along theroadway; and on the vehicle I provide electro-mechanical apparatusincluding means cooperating with the strip, and particularly its edgeportions, in such a way that as long as the vehicle is running normallyover the strip the steering gear will be unaffected, but when itdeviates from the line the electromechanical apparatus is immediatelyaffected, and proceeds to move the steering mechanism in the properdirection to bring the vehicle back into line over the strip.

Another object of the invention is to provide a simple method andapparatus for utilizing rays reflected from a strip or band, foreffecting the automatic steering of a vehicle such as an automobile, andmaintaining the same in line over such a band extending along a roadway.

In accomplishing the above objects, a further object is to provide meansfor projecting rays onto a reflecting guide-strip so that the points ofimpingement of the instant rays onto the guide-strip are so related thatif a portion of the rays projected onto the guide-strip should fail toimpinge upon the guide-strip, the steering mechanism of the vehicle willautomatically be affected to steer the vehicle and bring it back into asubstantially central and aligned position over the guide-strip.

In practicing the invention, I prefer to employ two distinct light raysor beams, one of which is projected onto the guide-strip near an edge ofthe guide-strip, and the other of which is projected onto another edgeof the guide-strip at a point located in a forwardly disposed positionwith respect to the first-named ray or beam; and one of the objects ofmy invention is to provide means whereby the reflected rays, through theagency of electric circuits, are utilized to maintain a control memberor valve normally in a mid position, which of course would correspond toa proper central position of the vehicle directly over the guide-strip,and with its longitudinal axis substantially coinciding with thevertical plane extending through the central axis of the guide-strip;and to maintain normally a condi- 5 tion of balance between devices inbranch electric circuits corresponding to each of the rays, operating insuch a way that if the vehicle becomes out of line over the guide-strip,one of the points of impingement of one of the rays will pass off of thereflecting area of the guide-strip, thereby developing an unbalancewhich I utilize to affect the steering mechanism to bring the vehicleback into proper alignment over the guide strip.

In the preferred embodiment of the invention, I employ a steering deviceor fluid-operated cylinder for controlling steering gear, and thissteering device, in the operation of the apparatus, is controlledthrough the agency of the two branch 20 circuits controlled by the tworeflected rays; and

one of the objects of the invention is to provide means associated withthis actuating device or steering cylinder, that will enable itsautomatic operation through the agency of the rays to be 5 inhibited toprevent the same from interfering with regular hand-steering of thevehicle whenever it may be necessary or advisable to steer the vehicleby hand.

Another object of the invention is to provide improved relief meansassociated with the steering cylinder and inhibiting device, which willprevent any possibility of pressure being built up in the steeringcylinder above a predetermined limit with which the cylinder is intendedto operate, the general purpose being to prevent too sudden actuation ofthe steering means, which of course might cause an accident. In this wayI attain the purpose of having the apparatus operate generally by makingvery slight corrections in the position of the steering wheels ormechanism, rather than to operate by making relatively large movementsof the steering gear; in other words, the apparatus and method operateto make slight and continual corrections in the position of the steeringgear to maintain the vehicle running in line over the guide-stripwhenever the vehicle has made any deviation from its course, sufiicientto bring the impinging point of a portion of the rays off of thereflecting surface of the strip.

Further objects of the invention will appear hereinafter.

The invention consists in the novel parts and combination of parts, andalso in the novel combination of steps, all of which contribute toproduce an emcient apparatus and method for effecting the automaticsteering of a vehicle on a roadway.

A preferred embodiment of the invention is described in the followingspecification, while the broad scope of the invention is pointed out inthe appended claims.

In the drawing:

Fig. 1 is a diagrammatic plan of the apparatus, a portion of which isshown in plan, while much of it is shown in horizontal cross-section.This view illustrates the forward wheels and steering gear of a vehiclesuch as an automobile, to which the apparatus as illustrated, isapplied. Fig. 1 also indicates the position and relation of the guidestrip on the roadway, to the vehicle when it is running in line with thestrip.

Fig. 2 is a front elevation of an automobile, and illustrating the meansfor projecting and reflecting the light rays from the car and back tothe car, for effecting the control of the steering of the car.

Fig. 3 is a perspective showing a view of a truck and trailer, theforward portion of the truck being broken away to indicate the point atwhich the light-ray devices would be installed so as to maintain thetruck in line with the guide-band in the lane on which the truck andtrailer are running.

Fig. 4 is a view of a diagrammatic nature, graphically illustrating away in which the position of the point of impingement of the light rayson the roadway controls the steering of the vehicle.

Before describing the invention more in detail, it should be understoodthat broadly it consists of a control apparatus involving the use of anelongated guide cooperating with means for projecting two rays or beamsof light onto the guide means, one of the points of impingement of thelight being adjacent one edge of the guide means and the other adjacentthe other edge of the guide means. If, in the operation of the controlpart one of the points of impingement or light spots is caused to passpartially or completely off of the guide means, the apparatus will thenbe affected to effect the control. In order to accomplish this I employtwo branch circuits in each of which there is a light sensitiveresistance which cooperates with its corresponding ray or beam referredto above. By balancing the force of the electric current in these twobranch circuits against each other, I am enabled to provide a controlapparatus capable of use for any desired specific purpose that dependsfor its action and operation upon whether either or both of the lightspots are impinging on the elongated guide-means. Although thisinvention can be used in many situations, I have described it in thepresent specification as applied to the steering of a vehicle along aroadway.

Referring particularly to Figs. 1 and 2, I indicates an axle of thevehicle, preferably the front axle, the ends of which are provided withsteering knuckles 2 having steering arms 3. Each of these arms isconnected up by an adjustable link 4 to a lever 5, the fulcrum pin 6 ofwhich is on the end of a fixed bracket 1 that may be attached to therear side of the axle. The rear arms of the levers are connected by alink 8. In applying my invention to such a vehicle steering apparatus, Iprovide means for shifting the link 8 to move the wheels 9 on the axesof their steering knuckles 2, and in order to accomplish this, I providea fluidoperated power device which, in the present instance, consists ofa fluid-operated cylinder I0 having a piston II within it, which isnormally located at an intermediate point in the cylinder. This point isnormally the middle point in the length of the cylinder, and the pistonH carries a piston rod 12 that extends through a stuffingbox l3 at theinner end of the cylinder so as to be attached to a rigid arm I4 thatprojects laterally from the link 8. The outer end of the cylinder 10 maybe supported on a vertical pivot pin l5 to permit the inboard end of thecylinder to swing slightly in a fore-and-aft direction when the link 8is shifted. This is necessary on account of the fact that the ends ofthe link 8 rotate about the pivot points 6. The pivot pin [5 for thecylinder may be attached to a bracket 1 B that is secured to the side ofthe frame member I! of the vehicle frame.

In accordance with my invention, I provide means for admitting fluidunder pressure to either end of the cylinder l0, depending upon thedirection of the necessary steering movement that must be given to thewheels 9 to correct their position and maintain the body of the vehiclerunning in line with the guideband l8 that extends longitudinally alongthe roadway l9, and in the middle of the lane along which the vehicletravels.

For this purpose at a suitable point on the vehicle, for example, at thefront axle I, I provide means for projecting light rays onto theguidestrip I8. This guide-strip must have a surface capable ofreflecting the rays projected upon it. For this purpose an ordinarywhite band such as now used on roadways for marking lanes, is found tobe satisfactory. The means for projecting the rays preferably comprisestwo electric illuminating devices or lamps 20 and 2|. As illustrated inFig. 1, the lamp 20 is located on the forward side of the axle I. and isin the form of a tubular lens box carrying condensing lenses forfocusing a ray or beam 22 down onto the guidestrip H3 in an inclineddirection as illustrated in Fig. 2, and this ray is reflected up fromits point of impingement indicated by the circle or spot 23. From thisreflecting point 23 the ray is reflected up onto a light-sensitiveelement such as a selenium cell or photoelectric cell 24 of any desiredtype. The lamp 2| back of the axle is mounted in the same way as thelamp 20, and throws a condensed light ray or beam down onto the strip 18at the spot 25 from which this ray is reflected up onto a selenium cellor photoelectric cell 26. In this connection it should be understoodthat an type of light-sensitive device may be employed, capable ofcausin a change in the resistance to a current flowing in two branchcircuits 2'1 and 28 that connect up to the lightsensitive devices 24 and26. The lamps and lightsensitive devices are positioned so that thelight spots 23 and 25 are located respectively near to different edgesof the guide-band, and also so that one of these spots is in advance ofthe other with respect to the direction of travel of the vehicle on theroadway.

With this arrangement it will be evident that if the vehicle in itscourse, tends to deviate toward the left as it travels along theroadwayin the direction of the arrow indicated in Fig. 1, the light spot23 will pass off of the reflecting surfaces or area of the strip [8, andthis will increase the resistance to the current passing in the branchcircuit 21 as compared with the current passing in the branch circuit28.

In practicing the invention, I balance these two currents against eachother in suitable apparatus, and I utilize any unbalance existing inthese two branch circuits as compared with each other, to eifect theproper movement in the steering apparatus for the wheels 9 to guide thevehicle back into line with the strip I8. In accomplishing this it isnecessary to employ an amplifier 29 which may be energized by anysuitable source of E. M. F. such as a battery 30 connected into acircuit 3| that connects up to the terminals 32.

The branch circuit 21 includes a section 21a on the output side of theamplifier, which is connected to a solenoid 33, and similarly the branchcircuit 28 includes a section 280. that is connected up to the coil of asolenoid 34. These solenoids control means for admitting fluid underpressure to the cylinder I9, and in the present instance, this meansconsists of a Valve device 35 having an elongated casing or barrel 36 inwhich a balanced piston valve is mounted to slide, said piston valvehaving a piston rod 31 the ends of which project into the coils of thesolenoids 33 and 34, and part way through the same. The piston valveincludes two piston heads 38 and 39 rigidly secured on the piston rod31, and in the normal and neutral position of this valve, these twopiston heads 38 and 39 cover outlet ports through the valve casing 36,that are connected up to inlet ducts or hose 40 and 4| that lead over tothe block or casing 42 of which the cylinder l forms a part.

The hose 49 and 4| connect through the cover plate 43 on the casing 42,to inlet ports 44 and 45 that lead into the interior of the cylinder 0.The central chamber of the piston valve casing 36 is supplied with fluidunder pressure through a supply pipe or hose 46 that leads to the samefrom a filter 41, said filter being supplied with fluid under pressurefrom a pump 48 through a delivery pipe 49 that delivers the fluidthrough a pressurecontrolled device 50 that delivers the fluid underpressure through a delivery pipe into the filter, said pressure devicebeing provided with a lateral by-pass pipe 52 not under pressure, thatleads excess fluid such as operating oil or similar fluid over to a sumpor reservoir 53.

In addition to the heads 38 and 39 on the piston rod 31, two remoteheads 54 and 55 are provided that are similar to the heads 38 and 39,and the space between the head 38 and 54 is connected to a branch outletpipe 56 that connects to a return pipe 51, which return pipe is alsoconnected through the casing 36 of this valve so that these two outlets56 and 51 lead off from the interior of the casing 36 beyond the pistonheads or valve heads 38 and 39.

In order to hold the piston rod 31 with its heads 38 and 39 normally ina neutral position, I provide yielding means connected with the pistonrod for this purpose. In the present instance, this yielding means is inthe form of a convoluted disc 58, the outer edge of which is held in afixed frame 59 and the center of which is attached to a collar 60rigidly secured on the piston rod 31. In Fig. 1 this disc is shownpulled slightly toward the right as though the current through thesolenoid 34 has become substantially de-energized by reason of the factthat the light spot 23 has passed off of the area of the strip l8, asillustrated in Fig. l.

The casing 36 is provided with vent ports 6| and '62, the former ofwhich connects up to the inlet port or hose 49 and leads from theadjacent end of the casing 36 beyond the piston head 54. The port 62 issimilarly located but leads from the opposite end of this casing 36.These vent ports 6| and 62 prevent accumulation of fluid in the ends ofthe casing, in such a way as to interfere with the free movement of thepiston rod 31 under the action of the solenoids.

The operation of my method, and the apparatus as described above, isillustrated in Fig. 1, which shows the piston valve moved from itsneutral position toward the right. This movement would be occasioned bythe light spot 23 passing ofi of the strip l8, as indicated in Fig, 1.When the piston valve moves over to the right to a position such as thatindicated in Fig. 1, the outlet hose 4| will be immediately suppliedwith liquid under pressure, which will pass to the inlet port 45 for thecylinder Ill, developing pressure in the right end of the cylinder l0,and this will move the piston toward the left by shifting the link 8toward the left as indicated by the arrow in Fig. 1. This will tend toswing the wheels 9 in the direction indicated by the arrows near them,and this will guide the vehicle back into alignment with the strip |8.If the vehicle deviates from its proper course, toward the right of theroadway, the light spot 25 would pass oil from the strip I8, and anopposite effect would be occasioned in the solenoids 33 and 34, causingshifting of the piston valve heads 38 and 39 toward the left, whichwould admit the operating fluid to the inlet hose 40 instead of the hose4|. This would admit the operating fluid through the port 44 into theleft end of the cylinder l0 instead of the right end, thereby developingan opposite steering efiect that would swing the wheels 9 in a directionopposite to that indicated by their arrows, to bring the vehicle backinto line with the strip l8.

In either case, when the piston valve is shifted to the right or to theleft as described above, this valve will open communication to thereturn pipe 51 so that any liquid in the end of the cylinder towardwhich the piston H is moved, will find outlet through the valve casing36 back to the sump 53.

This apparatus is preferably provided. with means operatable at will, toinhibit the operation of the cylinder I0 if it is desired to steer thevehicle by hand. In order to accomplish this, it is merely necessary toprovide a by-pass for the fluid in the ends of the cylinder Ill, so thatwhen the fluid is forced out of one end of the cylinder by movement ofthe piston I, it can pass around into the other end, If, in the designof an automobile provided with this apparatus, it is possible to locatethe cylinder I6 in a convenient position so that a valved by-pass portbetween the ends of the cylinder l9, could be opened from the driversposition, this could be done in practicing this invention; but as thecylinder I0 in practice, would probably be located in an inaccessibleposition, I have illustrated means for utilizing the pressure existingin the pipe system to control the establishment of such a bypass. Inother words, I provide for a remote control through the agency of thepressure existing in the pipe system or hose system. For this purpose,in the casing 42 I provide an inhibitor device which includes a bore 63,the inner end of which forms a pressure chamber 64 to which fluid underpressure is normally admitted through a pipe connection or hoseconnection 65, the operating end of this hose connection 65 beingconnected to a three-way valve 66. The fluid pressure in the chamber 64exerts its force against a movable member or piston 51 in the bore 63,and this piston has a circumferential port 68 which is normally held bythe pressure in the chamber 64 out of line with a cross port 69 thatconnects the two inlet ports 44 and 45 that communicate with the ends ofthe cylinder l0.

At the other side of this piston 61, resilient means in the form of acoil spring 10 is provided, which is a compression spring and normallyheld in a state of compression. However, if the pressure in the chamber64 becomes relieved, then the spring 10 will move the piston 61 towardthe forward end of the chamber 64 as illustrated in Fig. 1, and thiswill bring the circumferential groove 68 into line with the cross-port69. This will of course open communication between the ends of thecylinder ill.

The valve 66 to which the pipe or hose 65 connects, has a port connectedup to a pipe connection or hose H that leads over to it from the fluidsupply pipe 46 leading from the filter 41; and the port and the plug ofthis valve 66 in its normal position, connects this pipe H to the pipe65, thereby supplyin liquid under pressure to the chamber 64.

However, if the lever of this valve, indicated by the dotted line 12, isswun back as indicated by its arrow, to the "ofi position, then the portin this valve plug will open up communication between the pipe or hose65 and return pipe 13 that leads back to the sump 53. This will isolatethe cylinder 10 from the pressure system, and permit free movement ofthe piston l I in the cylinder [0.

Any suitable means can be employed for connecting up a hand-steeringgear to the wheels 9 for steering them. If desired, such a hand-steeringmechanism can include a link 14, one end of which is pivotally connectedto the arm I4.

The cylinder I and its piston II will not prevent the use ofhand-steering at any time, to override the automatic steering, by reasonof the presence of two spring pressed ball type valves 15 and 16,located respectively in by-pass passages TI and 18 that connect theducts 44 and 45. One of these check-valves is a relief for flow in onedirection while the other relieves for flow in the other direction.

In Fig. 4 I illustrate graphically the manner in which the position ofthe reflected light spots on the strip l8, control the steering gear ofthe car. B1, B2, C1, C2. In the diagram A, both spots 23 and 25 are onthe strip 18. In B1, the spot 23 is partly over the edge of the stripI8, which would seriously reduce the strength of the current passingthrough the coil of the solenoid 33, which would enable the solenoid 34to pull the piston valve heads 38 and 39 over toward the position inwhich they are illustrated in Fig. 1. Thi would swing the wheels 9toward the right as indicated by their arrows in Fig. 1, and bring thecar back into line over the strip. This pulling action is indicated bythe arrows in the small diagrams B1 and B2. The diagram B2 indicates theposition of the wheels after the automatic steering apparatus hascommenced to operate. The diagram C1 illustrates the light spot 25 ashaving moved off of the right-hand edge of the strip, while the spot 23is still on the strip. This would cause the solenoid controls to exert asteering movement on the wheels as indicated by the small arrow in Fig.4, thereby turning the wheels toward the position shown in the diagramC2, which would bring the body of the car back into alignment with thestrip.

In the operation of these light spots, it should This Fig. 4 includesseparate diagram A,

8 be understood that they would have the power and area to enable themto substantially aflect the solenoids even if the light spots were onlypartially oif of the reflecting area oi. the strip.

Special attention is called to the direction in which the downwardlydirected ray impinges upon the guide strip. By reason of the fact thatthe direction of this ray is inclined to the vertical line,substantially all the ray is reflected onto the photoelectric cell thatis cooperating with that particular ray projecting means. The eificiencyof reflection is increased due to this inclined direction in which theray impinges upon the guide strip.

Although I have described and illustrated a simple narrow strip i8 as acontrol or guide-strip for the apparatus, it should be understood thatthis strip may be made as wide or as narrow as may be desired, andvariations in the character of this strip could be made While stillpracticing the invention.

Many other embodiments of the invention may be resorted to withoutdeparting from the spirit of the invention.

What I claim is:

1. In vehicle guiding apparatus for guiding a vehicle passing along aroadway, the combination of a reflecting guide-strip of substantiallyuniform width extending along the roadway, means for projecting a ray oflight onto the guide-strip adjacent one edge thereof so that the ray isreflected from the same, a second means for projecting a ray of lightonto the guide-strip adjacent another edge thereof so as to be reflectedfrom the same, located forward, or aft, behind, the first-named means, alight-sensitive element upon which the first named light ray normallyimpinges to form a lighted spot on the guide strip when the vehicle isrunning normally in line with the said strip, a second light-sensitiveelement upon which the other ray impinges to form a lighted spot on theguide strip when the vehicle is running normally in line with saidstrip, electric circuit means including a branch-circuit correspondingto each of said light-sensitive elements, and connected to the same, andmeans controlled by said electric means through the agency of saidbranchcircuits for maintaining the vehicle in line with said guide-stripthe said fore and aft relative positions of said light projecting meansoperating to displace one or the other of the said light spots from theguide strip when the vehicle becomes out of the line with the guidestrip.

2. In vehicle guiding apparatus for guiding a vehicle having a pair ofsteering wheels, in passing along a roadway, the combination of areflecting guide-strip of substantially uniform width extending alongthe roadway, means carried on the vehicle for projecting a ray of lightonto the guide-strip adjacent an edge thereof so that the ray isreflected from the strip back toward the vehicle, a second means forprojecting a ray of light onto the guide-strip adjacent another edge ofthe strip, at a spot forward or aft with relation to the spot ofimpingement of the first-named ray and so as to be reflected from thstrip, a light-sensitive element upon which the first named light raynormally impinges when the vehicle is running normally in line with saidstrip, a second light-sensitive element upon which the other rayimpinges when the vehicle is running normally in line with said strip,electric-circuit means including a branchcircuit corresponding to eachof said light-sensitive elements and connected to the same, and meanscontrolled by said electric means connected to the steering wheels formoving the same to steer the vehicle into line over the strip when thelongitudinal aXis of the vehicle gets out of substantial parallelismwith the axis of the strip so that either of said light rays impingesupon the roadway oil of the area of said guide-strip.

3. In a vehicle control apparatus for guiding a vehicle passing along aroadway, th'e combination of a reflecting guide-strip extending alongthe roadway, means for projecting rays of light onto the guide-strip sothat they are reflected from the same, an electric-circuit includinglightsensitive means mounted in the path of the reflected rays, a pipesystem including fluid-operated means connected into the pipe system forcontrolling the steering of the vehicle, a valve for controlling theflow of fluid to the fluidoperated means, means connected with theelectrio-circuit for normally maintaining the valve in a neutralposition and controlled through the agency of th said light-sensitivemeans, all of said parts cooperating when a portion of the rays of lightfails to impinge on the guide-strip, to move the valve in a directionthat will steer the vehicle back into line with the guide-strip; a valvein the pipe system movable at will, and mean controlled by said valvefor inhibiting the operation of said fluid-operated means so as toprevent the fluid-operated means from interfering with steering thevehicle by hand.

4. A vehicle automatic control apparatus according to claim 3, in whichthe fluid-operated means consists of a cylinder with a piston normallylocated at an intermediate point in the length of the cylinder when thevehicle is running normally in line with the guide-strip, and in whichthe means controlled by the hand-operated valve for inhibiting theautomatic steering includes a pressure-controlled part to which thefluid under pressure is admitted, and by-pass ports controlled by thesaid pressure-controlled part for opening communication between the endsof the cylinder when the steering is to be accomplished by hand.

5. In a vehicle control apparatus for guiding a vehicle passing along aroadway, the combination of a reflecting guide-strip extending along theroadway, means for projecting rays of light onto the guide-strip so thatthey are reflected from the same, an electric-circuit includinglight-sensitive means mounted in the path of the reflected rays, a pipesystem including a fluid-operated cylinder with a piston therein, withmeans to connect the same to steering means of the vehicle to controlthe same, means for controlling the flow of the operating fluid to thesaid cylinder, means connected into th said electriccircuit for normallymaintaining said last named means in a neutra1 position and controlledthrough the agency of said light-sensitive means, all of said partscooperating when a portion of the rays of light fails to impinge on theguidestrip, to move the fluid-controlled means in a direction that willadmit fluid to the said cylinder to enable the said piston to efiect thesteering of the vehicle back into line with the guidestrip, amanually-controlled valve connected into the pipe system, movable atwill, and an inhibitor-device associated with the cylinder, having portsfor the fluid and including means controlled by the pressure in the pipesystem for normally holding the inhibitor-device in a condition topermit operation and control of the said cylinder through the agency ofsaid lightsensitive means, and a spring associated therewith foractuating the inhibitor-device when the fluid pressure within the sameis relieved, to control said ports to open communication between theends of said cylinder, and thereby permit free movement of the piston,so as to prevent the fluid-operated cylinder from interfering withsteering the vehicle by hand.

6. In an automatic control apparatus for steering a Vehicle having asteered wheel or wheels, the combination of a pipe-system for conductingfluid under pressure, a steering cylinder connected to the pipe-system,vhaving a piston normally disposed in an intermediate position in thecylinder, and having means connecting the same with the steered Wheel orwheels, for steering the vehicle, a valve for controlling the admissionof the fluid under pressure to either end of said ,cylinder, aninhibitor device associated with said cylinder, including a pressurechamber and a pressure-controlled member therein, said inhibitor deviceand cylinder having by-pass ports capable of opening communicationbetween the ends of the cylinder; and means for controlling the flow offluid pressure to said chamber to control the position of the saidmovable member therein.

'7. An automatic steering apparatus according to claim 6, includingresilient means associated with the movable member of said inhibitingdevice for opposing the fluid pressure acting upon the same, andoperating when the pressure fluid is cut ofi, to move the said movablemember in the said chamber andthereby efiect communication between theends of the steering cylinder.

8. An automatic steering apparatus according to claim 6, including anadmission port corresponding to each end of the cylinder for admittingthe operating fluid into the same, and having a pressure relief portincluding a springpressed relief-valve leading from each admission portover to the opposite admission port.

VICTOR H. SEVERY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

